1. Field
The present disclosed embodiments relate generally to wireless mobile computing devices, and more specifically to power savings in the same relative to idling the modem.
2. Background
Mobile communication devices including devices such as smartphones, tablet computers, gaming devices, and laptop computers are now ubiquitous. A common and ongoing issue with these types of devices is power management. More specifically, these types of devices continue to develop more advanced processing resources, displays, and communication systems that demand more and more power.
Although advances continue to be made in the areas of battery technology and hardware efficiency, these advances do not directly address the users' experience when a mobile device is operating under power constraints. As a consequence, the current mobile device power management techniques are not adequate to meet user expectations and will almost certainly not be satisfactory in the future.
One aspect of power management involves idling of the modem when not needed. The Radio Resource Control (RRC) protocol is responsible for assigning radio resources between the user equipment (UE) and the network (see the 3rd Generation Partnership Project (3GPP), “Radio Resource Control (RRC) Protocol Specification”, Tech. Spec. 25.331, 2006). The RRC states in WCDMA packet data are illustrated in FIG. 2, and are described below (similar states apply to GSM and EvDO/DO networks).
FIG. 2 illustrates various radio or modem modes of a typical user equipment (UE). Generally, a UE has an active state 202 and an idle state 204. Within the active state 202 there can be three sub-modes: CELL_DCH 206, CELL_FACH 208, and CELL_PCH 210. In some cases, a fourth sub-mode can also exist (not illustrated).
Idle state 204 consumes less power than the active state 202 or any of the sub-modes of the active state 202. This is because the UE does not have an RRC connection and thus the UE does not transmit in this mode, or transmits only rarely (e.g., Location Area Updates and Routing Area Updates, which are infrequent). The UE can still have an IP address (i.e., a PDP context) and it can be reached by paging, but the connection must be reestablished before data can be transmitted from the UE. Because the UE is required to monitor the paging channel only at intervals, the modem does not need to be continuously on, but will instead enter the active state periodically. The trade-off for this is greater latency to send/receive data. However, if this latency is not too great, the advantages of being in the idle state and saving battery power outweigh the disadvantages of the greater connection latency.
The network typically controls the RRC state, and since the network may not know when the UE has completed a given data exchange, it typically keeps the RRC connection active for some fixed time delay in anticipation of more data to/from the UE. The problem with this is that the modem stays in an active state often after data transmission has ceased, thus wasting power.
There is therefore a need in the art for systems and methods to determine a dynamic time delay after which the RRC connection is to be transitioned to an idle state.